An indexable type cutting tool having a cutting insert attached to a holder has conventionally been used as a cutting tool for use in a cutting process or the like. The cutting insert used in this cutting tool generally has an upper surface, a lower surface, and a side surface, and has a cutting edge formed along an intersection of the upper surface and the side surface. A workpiece, such as a metal member, is cuttable by bringing the cutting edge into contact with the workpiece being rotated.
As a cutting insert, for example, Japanese Unexamined Patent Publication No. 2009-208216 (Patent Document 1) has proposed a cutting tip having, on an upper surface thereof, a projection with which chips of a workpiece come into contact. In the cutting insert described in Patent Document 1, the chips of the workpiece can be curved by being brought into contact with a first ridge and a second ridge extending from the first ridge.
In a low feed machining at a low feed rate, chips flow along the upper surface. Therefore, when used the cutting insert described in Patent Document 1, the chips can be brought into contact with the first ridge and the second ridge. However, in a high feed machining at a high feed rate, the chips rise and flow from the cutting edge in a direction approximately horizontal to the lower surface, and hence the chips flow away from the upper surface. Consequently, the chips may contact only with the first ridge without contacting with the second ridge. On that occasion, only a single point, namely, a front end of the first ridge comes into contact with the chips. This makes a chip flow unstable, thus leading to low stability of chip disposal.
The present invention has been made in view of the foregoing circumstances and is aimed at providing a cutting insert, a cutting tool, and a method of producing a machined product, all of which ensure stable chip disposal during both the low feed machining and the high feed machining.